Electron gun apparatus with heat sink means for supporting filament and grid



D. A. JONES ELECTRON GUN APPARATUS WITH HEAT SINK MEANS July 4, 1967 FOR SUPPORTING FILAMENT AND GRID Filed March 26, 1965 2 Sheets-Sheet l INVENTOR BY ES f/w/CKAJON D. A. JONES July 4, 1967 3,329,849 ELECTRON GUN APPARATUS WITH HEAT SINK MEANS l y FOR SUPPORTING FILAMENT AND GRID Filed March 26, 1965 2 Sheets-Sheet 2 l INVENTOR. BYf/Q/CKA. J ON ES United States Patent O ELECTRUN GUN APPARATUS WITH HEAT SINK IANS FOR SUPPORTING FILAMENT AND Derrick A. Jones, Somerset Township, St. Croix County, Wis., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Mar. 26, 1965, Ser. No. 442,902 7 Claims. (Cl. 313-82) This invention relates to improvements in electron guns.

In one aspect, this invention relates to an electron g-un construction having a new massive heat sink and a simplified mounting of filament and grid.

In another aspect, a gun is provided which has superior filament life.

As those skilled in the art will appreciate, conventional electron guns comprise a filament, a grid, and an anode generally axially aligned with respect to one another by appropriate mounting means, the Whole assembly being enclosed in an appropriate evacuatable housing. Heretofore, the relationship between these components, and especially the manner in which they are mounted with respect to one another within the housing, has been such that all known guns change their characteristic electron emission properties as the gun warms up in use. This change in beam characteristics is caused both by the thermal'expansion and by the thermal contraction associated with various parts of the gun system relative to one another. Such change is especially caused by the mounting means heretofore employed to position the filament and the grid in a gun.

By the present invention a new combination is provided which avoids most of the problems heretofore associated with thermal expansion and contraction in electron guns. This new combination is generally directed towards maintaining in an electron gun a predetermined and uniform relationship between the electron emitting area and the grid aperture.

It is accordingly an object of the present invention to provide an electron gun having relatively low thermal drift characteristics so that electron beam spot size and associated characteristics can be Very carefully and continuously controlled during an entire gun operating time span.

Another object of this invention is to provide an electron gun assembly in which both the filament and the grid are mounted yupon a heat sink.

Another object -of this invention is to provide an electron beam construction having an air cooled, massive heat sink which is adapted to support the posts of a hairpin filament and which is further adapted to support a grid.

Another object of this invention is to provide an electron gun construction wherein both thermal distortion and ion erosion of filament legs is minimized.

Another object of this invention is to minimize thermal distortion of the hairpin filament in an electron gun.

Another object of this invention is to minimize thermal distortion in an electron gun by using a current carrying massive heat sink to support a hairpin type filament.

Another -object of this invention is to create a predetermined emitting area in a hairpin filament by selectively fiattening the apex region of such a filament in an electron beam gun construction of the type indicated.

Another object of this invention is to construct an electron gun wherein there is a predetermined and uniform relationship maintained between the electron emitting filament and the grid aperture.

Another object of this invention is to form a heat sink for use in an electron gun construction comprising two 3,329,849 Patented July 4, 1967.

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similar aluminum sections which have their surfaces appropriately anodized and which are bonded together to form the desired heat sink by means of an electrically insulating epoxy resin cement or the like.

Other and further objects of this invention will become apparent to those skilled in the art from a reading of the present specification taken together with the accompanying diagrammatic drawings wherein:

FIGURE 1 is a partially exploded perspective view of one embodiment of the present invention;

FIGURE 2 is a top plan view taken along the line 2 2 of FIGURE 1;

FIGURE 3 is a vertical sectional view taken approximately along the line 3 3 of FIGURE 2;

FIGURE 4 is a plan view taken along the line 4-4 of FIGURE 1;

FIGURE 5 is a transverse enlarged sectional view taken approximately along the line 5 5 of FIGURE 3;

FIGURE 6 is an enlarged vertical sectional view taken approximately along the line 6 6 of FIGURE 4, edge portions thereof broken away;

FIGURE 7 is an enlarged vertical sectional view taken approximately along the line 7 7 of FIGURE 2, some edge portions thereof broken away;

FIGURE 8 is an exploded view of the filament construction used in the embodiments shown in the figures.

FIGURE 9 is an alternate embodiment of the center region of FIGURE 4;

FIGURE l0 is an enlarged vertical sectional View taken approximately along the line 10-10 of FIGURE 9; and

FIGURE 11 is an enlarged vertical sectional view of the central portion of shroud element 80.

Electron guns of this invention are of the type having axially aligned filament, grid and anode components.

Turning to FIGURES 1 through 8 there is seen an embodiment of an electron gun construction of this invention herein designated in its entirety by the numeral 10. 'I'lie gun 10 is seen to utilize three main structural components: A heat sink 14, an anode s-upport 15A, and a spacer element 13.

The heat sink 14 is composed of a pair of halves 14A and 14B and of a continuous layer 16 of solid, thermally stable, electrically non-conductive material (see FIG- URE 6). Layer 16 is preferably as thin as practicable. Each half 14A and 14B is composed of solid, thermally stable, electrically conductive material such as metal or the like, preferably aluminum. Halves 14A and 14B are each equipped with cooling means.

In the embodiment shown in FIGURES 1 through 8 (see FIGURE 3) such cooling is provided by air cooling with radially extending, axially spaced, parallelly positioned fins 17 (associated with half 14A) and fins 18 (associated with half 14B). Instead of being air cooled, it will be appreciated that the ihalves 14A and 14B can be liquid cooled lby circulating a liquid through appropriate passageways (not shown) in heat sink 14.

The halves 14A and 14B are so Iconstructed as t0 enable their respective forward end portions 82 and 83, respectively, to meet at the alignment axis 19 of gun 10. In this embodiment, the center or axis of halves 14A and 14B coincides -with the alignment axis 19 of gun 10, but it will be appreciated that in general the halves 14A and 14B need only come into close, mating proximity to one another at one point 21, point 21 being on the axis 19 at the forward end of heat sink 14. In general, it is preferred that the center axis of heat sink 14 coincide with the alignment axis 19 of gun 10 at point 21.

Layer 16 can be composed of any conventional solid, thermally stable, electrically non-conductive material. When the halves 14A and 14B are constructed of a metal such as aluminum, it is convenient to anodize the surface poitions of the aluminum so as to leave a layer of aluminum oxide 22 and 23 on each respective half 14A and 14B. Such an anodized layer has excellent dielectric properties and it provides a good insulative barrier against the passage of electricity. To further compose the layer 16 (as shown in FIGURE 6), a layer Vof epoxy resin 24 can be placed between the layers 22 and 23. Such epoxy resin layer 24 not only serves to provide an additional non-conductive barrier between the halves 14A and 14B but also serves to bond and bind together half 14A to half 14B, thereby providing in this embodiment a heat sinlcwhich has a monolithic character. Those skilled in the art will appreciate t-hat, depending upon the manner of construction, it may be practical and convenient to bind the halves 14A and 14B together by an external clamping means, preferably non-conductive (not shown).

In spaced relationship to the layer 16 in each half 14A and 14B in the embodiment shown is provided a pair of channels 26 and 27 (one in each half 14A and 14B, respectively). These channels 26 and 27 are so positioned that a hypothetical line joining their centers passes through the axis 19 of gun 10. As those skilled in the art will appreciate, only one such channel is necessary in one or the other of the halves 14A and 14B; two channels are provided in the embodiment shown to aid in centering, as will be seen from the subsequent description below.

The anode support 15 is constructed of a solid, thermally stable, electrically conductive material such as a metal or the like, preferably aluminum. The anode support 15 in the embodiment shown is so constructed as to have a passage 28 formed therein which extends lengthwise and centrally therethrough. The passage 28 is so located as to be adapted for coaxial alignment with axis 19. In the embodiment shown, the anode support 15 can be considered to comprise a base portion or pad 29 which has integrally formed therewith, but rearwardly extending therefrom, a peripherally located, circumferentially extending spacer sleeve 64. Also, integrally formed with the pad 29' and rearwardly extending therefrom so as to define the walls of passage 28 is a supporting column 32. In the embodiment shown, observe that the supporting column 32 has a portion 33 of its inside Walls threaded. `In the spacer sleeve 64 is formed a hole or opening 34 so as to permit easy evacuation of the region or chamber 36 by a vacuum pump means (not shown) when the gun is to be made operational.

The spacer element 13 is formed of solid, thermally stable, electrically non-conductive material. It has defined therein a centrally located aperture 37. The spacer element 13 is adapted to maintain the anode support 15 in spaced relationship to the heat sink 14 and also to align axially the passage 28 with the `gun alignment axis 19. Thus, the spacer element 13 has its rear face 38 appropriately grooved to receive the forward portions of halves 14A and 14B and further has a shoulder 39 circumferentially formed in its forward face 41 for receipt of the spacer sleeve 64.

In the embodiment shown, the halves 14A and 14B, the layer 16, the spacer element 13 and the anode support are all constructed so as to be gas impermeable. In order to maintain a gas-tight relationship between the spacer element 13 and the adjoining heat sink 14 and anode support 15, the heat sink 14 and the `opposing face of the anode support 15 are each provided with an appropriate ygroove 42 and 43, respectively, into each of which is mounted a suitably dimensioned O-ring sealing member 44 and 45, respectively. Thus, in the assembled gun 10, the heat sink 14, the spacer element 13 and the anode support 15 can be exposed to the atmosphere during gun operation.

The anode support 15 is conveniently connected in gas-tight relationship to a tubular member or tube 74 which is associated with other equipment not shown. An O-ring sealing gasket 75 is lused to obtain a gas-tight seal between tube 74 and anode support 15. An electron beam generated by gun 10 can thus be led through tube 74 to a target area. The chamber 36 can be suitably evacuated during operation of gun 10' by means of vacuum pump means (not shown) connected to opening 34 in anode support 15.

Through the aligned holes 76 (paired) and 78 (paired) in heat sink 14 and spacer element 13 (respectively) it is convenient to extend an appropriate bolt and nut means (not shown) for mounting the spacer element 13 with the heat sink 14. The anode support 15 can be conveniently similarly secured to the spacer element 13 using bolt and nut means (not shown) which connect from the anode support 15 with the spacer element 13 using holes 88 (paired) which are spaced 910 degrees from the holes 78 in spacer element 13.

A hairpin-type filament 47, including an apex portion 49 and a pair of legs 48 depending therefrom, is mounted across the forward end of heat sink 14 so that one leg 48 is connected with sink half 14A and the other leg 48 is connected with sink half 14B. In the embodiment shown, such connection is secured by providing suitable holes in respective halves 14A and 14B adapted to laccommodate the respective leg 48 of filament 47 (see, for example, FIGURE 7). In order to fix the position of filament 47 relative to the heat sink 14, a pair of diametrically opposed, radially extending opposed bores 51 and 52 (in respective halves 14A and 14B) are provided. Each bore 51 and 52 connects with a leg 48 of filament 47. When plugs 53 (paired) are inserted one into each bore 51 and 52, respectively, and are thereafter pressured against each leg 48 by means of headless screws 54 (paired; one in each bore 51 and 52) the legs 48 are pinched or pressured against the Wall of each associated half 14A and 14B, respectively. Thus, the filament 47 is positioned in the heat sink 14.

Observe that the apex portion 49 of filament 47 is aligned with the axis 19 and that each leg 48 is thus electrically connected with a different one of said halves 14A and 14B. The hairpin filament 47 can be constructed of any conventional material known to the art of electron gun manufacture, such as tungsten (Wire or ribbon) or the like.

Once the filament is positioned or assembled in the heat sink 14, the resulting assembly is preferably placed in a suitable fixture device having an associated grinding means (not shown). A small fiat, planar area is then ground on the apex 49 of the filament. This planar area is positioned so as to have a close dimensional relationship to the alignment axis 19 of the gun 10 and to the grid 56. Thus, this flat area is normal to the gun alignment axis 19 and is also normal to the aperture or perforation 57 of the grid 56. Such a fiatted filament 47 (as shown in FIGURE 10) is used in preferred embodiments of this invention; a filament 47 with a flatted apex 49 in the electron gun construction 10 or 10 of the present invention concentrates the emission of electrons from the apex region 49 of the filament 47.

A plate-ilke grid 56, constructed of any suitable material known to the art of electron gun manufacture, such as stainless steel or the like, is provided. The central portion 58 of grid 56 in the embodiment shown in FIGURES 1 through 8 has a perforation 57 extending through its center. Observe that the central portion 58 is thinner than the adjoining peripheral portions.

In plan view, the grid 56 is generally ellipticaly shaped and near the respective opposite end portions of its long axis 61 are provided a pair of holes 62 (each of which is aligned with the long axis 61). Observe that the aperture or perforation 57 passes through the center of the grid 56 (and therefore lies along the long axis 61). In each hole (referring to FIGURE 8) is mounted a pin 63 (paired). Over each pin 63 is positioned a sleeve 64 (paired).

In assembling the electron gun 10, each pin 63 and an associated sleeve 64 is each mounted in a single channel 26 and 27 by means of cement 85 of epoxy resin or the like. A suitable jig (not shown) can be used to hold the pins 63 and the sleeve 64 in place during such cementing operation.

Observe that one pin 63 before being cemented in place is equipped with a conductive wire element 71 which is of sufiicient length to extend all the Way through such a channel as channel 26 and to protrude therefrom for subsequent electrical connection purposes. The grid 56, the pins 63 and the wire element 71 are constructed of electrically conductive material, but the sleeves 64 and the cement 85 are composed of electricallly nonconductive or insulative material.

After the sleeves 64 and the pins 63 are duly mounted in place, the protruding portion of each pin 63 is diametrically bored so as to provide a pair of .generally parallelly extending holes 67 and 68 transversely extending therethrough, one hole 68 being in each pin 63. The

position of each hole 68 is such that when the grid 56 is mounted over the protruding ends of the pins 63, each hole 68 aligns with a corresponding hole 67 in grid 56 so that the grid 56 can be properly spaced from the filament 47 and the heat sink 14. The grid 56 is maintained in such desired fixed position on the protruding ends of pin 63 by means of a length of wire 69 whose opposite end portions are bent so as to extend through the holes 68 and 67, thereby positioning the grid 56 in the desired' spatial position. The mid portion of the wire 69 in the assembled electron gun 10 can abut against adjoining portions of the spacer element 13 which thereby prevents wire 69 from being removed from holes 67 and 68.

To replace the grid or accomplish other repairs in the electron gun, the wire 69 in a disassembled gun is simply pulled away to remove the grid 56 from the heat sink 14.

Observe that the grid 56, owing to the method of construction, is thus easily centered over the filament 47. When the pins 63 and sleeves 64 are potted in the channels 26 and 27, further observe that the wire element 71 is also insulated from the walls of the half 14A (see FIGURE 3), so that an electric contact can be established with the grid 56 from the rear portion of the heat sink 14 when the gun is operational, thereby maintaining the grid 56 at the desired potential relative to the filament 47.

Those skilled in the art will appreciate that the design of the grid 56 is such as to minimize capacitance effects between the grid and the associated structure of the gun.

A generally cylindrically shaped anode 72 constructed of a conventional material known to those familiar with the art of electron gun manufacture, such as stainless steel or the like, is positioned within the passage 28. A portion 73 of the outer walls of anode 72 are threaded for mating engagement with the threaded portion 33 of supporting column 32 of the spacer element 13. Such threaded engagement not only permits a fixed relationship to be established between the anode 72 and the supporting column 32, but also enables one to select a desired fixed distance between the filament 47 and the anode 72. The rearmost portion of the anode 72 has a restricted mouth or aperture portion 90. This restricted aperture portion 90, as those skilled in the art of electron gun manufacture will appreciate, provides a desirable and preferred electric field for accelerating the stream of electrons leaving the region of the grid 56 in the electron gun 10.

Appropriate recesses are preferably provided in the spacer element 13 for countersinking the nuts and bolts (not shown) used to secure the heat sink 14 and the anode support 15 to the spacer element 13.

Turning to FIGURES 9 through 11 there is seen an alternative embodiment of an electron gun of the invention numbered in its entirety by the numeral 10.

A principal dierence between the embodiment shown in FIGURES 9 through 1l and that shown in FIGURES 1 through 8 lies in the addition of a filament shroud 80 which is positioned between the grid 56 land the heat sink 14. A pair of holes 81 in the shroud 80 are adapted to be aligned with the holes 62 in the grid 56 so that the pins 63 can be used to center not only the grid 56, but also the filament shroud relative to the heat sink 14 and the filament 47.

The filament shroud 80 is constructed using a wafer of solid, thermally stable, electrically conductive material; it can be suitably formed of a substance such as aluminum, stainless steel, molybdenum or the like. The surfaces of this wafer are generally coated with a thin layer 84 (see FIGURE 1l) of an electrically non-conductive material which insulates the shroud 80 from the filament 47, the grid 56, and one of the halves of the heat sink 14. This electrically insulative material can be of any conventional substance; however, when the shroud 80 is constructed of -a metal such as aluminum, it is usually convenient and satisfactory to construct the layer 84 by simply anodizing the surfaces of the wafer. The center of the filament shroud 80 is equipped with a central hole 81 into which the filament apex 49 and its associated legs 48 protrude (see FIGURE 10), the hole 81 being generally coaxially with the axis 19 of the gun 10.

The shroud 80 is electrically connected with one of the halves of heat sink 14. Such electrical connection can be conveniently achieved, as shown in FIGURE 9, by simply using a screw 89 which is adapted to make electrical connection with the shroud 80. As shown, screw 89 passes through a suitable uninsulated hole in shroud 80 into .appropriate threaded engagement with an uninsulated `channel (not shown) in one of the halves of heat sink 14.

The shroud 80 is so constructed as to shield the filament 47 from the grid 56. Shroud 80 restricts the movement of ions which tend to e-rode the filament legs 48 during operation of the gun 10'.

The purpose of the lip circumferentially extending about the hole 81 of the filament shroud 80 is to reduce electrical capacitance.

A section through the assembled gun 10 using a filament shroud 80 is shown in FIGURE 11, wherein the yshroud 80 is formed of .aluminum which has had its surfaces anodized so as to cover shroud 80 with a layer 84 of aluminum oxide. When the shroud 80 is formed of a material -other than aluminum, the layer 84 can beformed of some other suitable insulative material such .as an organic resin or the like.

In operation, a gun 10 or 10 each conventionally have the anode 72 -and the anode support 15 maintained substantially at ground potential. The heat sink 14, the filament and the grid are maintained at a high potential, say, 20,000 volts or higher as desired or as equipment design considerations indicate. A cur-rent is allowed to flow into one half of the heat sink through the filament 47 and from the other sink half. Electrical connection with the heat sink 14 can be accomplished by using the bolts (not shown) which extend through the holes 76 (see FIGURE 1). The appropriate potential for the grid 56 can be obtained by applying the desired potential to a binding post 77 which electrically is connected to the wire 71 (see FIG- URE 3).

Guns of this invention `are of the self-accelerating type by which reference is had to the fact that substantially the entire acceleration is imparted to electrons from the filament as they pass from the grid towards the anode. As electron gun operation is well know to those of ordinary skill in the art 4and forms no part of the present invention, a detailed description thereof is not given herein.

In conventional electron gun constructions, there is relative movement of the filament relative to the grid aperture. This results in changes of emission and unsymmetrical erosion of the filament. In the present invention, particularly when filament shroud 80 is used, substantially only 7 the emitting area of the filament surface is maintained at the electron emitting tempe-rature. This has the dual effect of minimizing the thermal distortion in, and of minimizing the concurrent ion erosion of, the filament leg surfaces. Ion erosion redu-ction is particularly important in many industrial applications where only relatively poor vacuum conditions are maintained during gun operation. IThe gas present under such conditions is sufiicient to accelerate ion erosion of a conventional filament compared to the situation where a gun can be continuously maintained in a high vacuum environment.

The distance between the holes into which the filament legs are inserted, in the guns of this invention, is kept minimal by reducing the insulation thickness of the heat sink in the region which separates the two halves carrying the filament leg holes. This enables the filament to be a simple hairpin configuration having very short sides and a sharp apex radius for efiicient electron radiation. Such filament construction contributes to the improved thermal stability associated with guns of this invention.

Guns of the present invention are generally readily demountable for cleaning, replacement of parts, etc., and, once demounted, corrections, alterations, repairs, etc., can be accomplished with a minimum of down time.

A convenient depth for anodizing aluminum surfaces used in the present invention ranges from about 0.002. inch to about 0.008 inch of A1203 (aluminum oxide). A preferred epoxy resin thickness for adhe-ring the two halves of a heat sink ranges from about 0.0002 to 0.001 inch. After the two halves are thus cemented together, they frequently can be conveniently machined to produce an accurate relationship between the halves.

It will be appreciated by those skilled in the art that many other embodiments and modifications in the present invention, other than those described above, can be made without departing from the spirit and scope thereof.

The claims are:

1. An electron gun of the type having axially aligned filament, grid and anode components, said gun comprising (a) a heat sink defined by a pair of halves both con-v structed of solid, thermally stable, electrically conductive material adapted to meet at their respective forward end portions on the alignment axis of such gun, each said half including cooling means, and `further defined by a continuous layer of solid, thermally stable, electrically non-conductive material positioned between said halves,

(b) a solid, thermally stable, electrically conductive anode support having a passage centrally defined therein,

(c) a solid, thermally stable, electrically non-conductive spacer element having an aperture centrally defined therein, said spacer element being adapted, both to maintain said anode support in spaced relationship to said heat sink and to align axially said passage of said anode support with said alignment axis,

(d) an electron gun filament including an apex portion and a pair of depending leg portions, each leg being electrically connected with a different one of said halves, said apex portion being aligned with said alignment axis,

(e) a grid assembly including a plate-like grid having a perforation through its central portion, said grid being positioned in proximity to said electron gun filament transversely across said gun axis so as to have said perforation coaxiall with said lgun axis, said assembly further including grid support means extending from said heat sink for positioning said grid and functionally electrically connecting said grid to an electrical potential, and

(f) an anode operably associated with said anode support generally coaxially With said gun axis.

2. The gun of claim 1 further having a filament shroud,

said filament shroud including a wafer of soilid thermally stable, electrically conductive material positioned between said grid and said heat sink including a hole centrally located therein, said hole being generally coaxial with said gun axis and having said filament apex protruding thereinto, and further including electrically non-conductive means insulating said wafer from said filament, said grid, and only one of said halves.

3. The gun of claim 1 further having grid support means including connecting means for detachably securing said grid thereto.

4. An electron gun having relatively low thermal drift characteristics and long term vfilament life characteristics of the type having axially aligned filament, grid and anode components, said gun comprising (a) a heat sink ydefined by a pair of metallic halves adapted to meet at their respective forward end portions on the axis of said gun, each said half including cooling means, and one of said halves having a generally axially extending channel defined therein,

(b) a continuous layer of solid, thermally stable, gas impermeable, electrically non-conductive material positioned between said halves,

(c) a metallic anode support having a passage centrally defined therein,

(d) a solid, thermally stable gas, impermeable, electrically non-conductive spacer element having an aperture centrally defined therein, said spacer element being adapted both to maintain said anode support in spaced relationship to said heat sink and to align axially said passage with said gun axis,

(e) a hairpin filament including an apex portion and a pair of depending legs, said apex portion being aligned wtih said gun axis and each one of said legs being electrically connected with a different one forward end of said halves,

(f) a plate-like grid having a perforation through its central portion, said grid being positioned in proximity to said filament transversely across said gun axis so as to have said perforation coaxial with said gun axis,

(g) grid support means extending between said grid and said heat sink including both electrically conductive conductor means extending from said grid through said channel and electrically non-conductive insulator means insulating said conductive means from said heat sink, said conductor means and said insulator means together forming a gas-impermeable seal with said heat sink,

(h) a generally cylindrically shaped anode functionally associated with said anode support and coaxial with said gun axis, and

(i) means for maintaining said heat sink, said layer,

said anode support, and said spacer in gas-impermeable relationship to one another.

5. The gun of claim 4 further having a filament shroud including a wafer of solid Ithermally stable, electrically conductive material positioned between said grid and said heat sink including a hole centrally located therein, said hole being generally coaxial with said gun axis and having said filament apex protruding thereinto, and further including electrically non-conductive means insulating said wafer from said filament, said grid, and only one of said halves.

6. An electron gun having long-term thermal drift characteristics and long term filament life characteristics of the type having axially aligned filament, -grid and anode components, said gun comprising (a) a heat sink defined by a pair of metallic halves adapted to meet at their respective forward end portions on the axis of said gun, each said half including cooling means, and one of said halves having a generally axially extending channel defined therein,

(b) a continuous layer of solid, thermally stable, gas impermeable, -electrically non-conductive material positioned between said halves,

(c) a metallic anode support having a passage centrally defined therein,

(d) a solid, thermally stable, gas impermeable, electrically non-conductive spacer element having an aperture centrally defined therein, said spacer element being adapted both to maintain said anode support in spaced relationship to said heat sink and to `align axially said passage with said gun axis,

(e) a hairpin filament including an apex portion and a pair of depending legs, said apex portion being aligned with said gun axis and each one of said legs being electrically connected with a different one forward end of said halves,

(f) a plate-like grid having a perforation through its central portion, said grid being positioned in proximity to said filament transversely across said gun axis so as to have said perforation coaxial with said gun axis,

(g) grid support means extending between said grid and said heat sink including both electrically conductive conductor means extending from said grid -through said channel and electrically non-conductive insulator means insulating said conductive means from said heat sink, said conductor means and said insulator means together forming a gas-impermeable seal with said heat sink,

(h) a generally cylindricailly shaped anode functionally 10 -associated with said anode support and coaxial with said gun axis,

(i) means for maintaining said heat sink, said layer,

said anode` support, and said spacer in gas-impermeable relationship to one another, and

(j) .a filament shroud including a wafer of solid thermally stable, electrically conductive material positioned between said grid and said heat sink including a hole centrally located therein, said hole being generally coaxial with said gun axis and having said filament apex protruding thereinto, and further including electrically non-conductive means insulating said wafer from said filament, said grid, and only one of said halves.

7. The gun of claim 6 further having grid support means References Cited UNITED STATES PATENTS 9/1958 Echo 313--271 6/1965 Sciaky 313-271 I AMES W. LAWRENCE, Primary Examiner.

25 V. LAFRANCHI, Assistant Examiner. 

1. AN ELECTRON GUN OF THE TYPE HAVING AXIALLY ALIGNED FILAMENT, GRID AND ANODE COMPONENTS, SAID GUN COMPRISING (A) A HEAT SINK DEFINED BY A PAIR OF HALVES BOTH CONSTRUCTED OF SOLID, THERMALLY STABLE, ELECTRICALLY CONDUCTIVE MATERIAL ADAPTED TO MEET AT THEIR RESPECTIVE FORWARD END PORTIONS ON THE ALIGNMENT AXIS OF SUCH GUN, EACH SAID HALF INCLUDING COOLING MEANS, AND FURTHER DEFINED BY A CONTINUOUS LAYER OF SOLID, THERMALLY STABLE, ELECTRICALLY NON-CONDUCTIVE MATERIAL POSITIONED BETWEEN SAID HALVES, (B) A SOLID, THERMALLY STABLE, ELECTRICALLY CONDUCTIVE ANODE SUPPORT HAVING A PASSAGE CENTRALLY DEFINED THEREIN, (C) A SOLID, THERMALLY STABLE, ELECTRICALLY NON-CONDUCTIVE SPACER ELEMENT HAVING AN APERTURE CENTRALLY DEFINED THEREIN, SAID SPACER ELEMENT BEING ADAPTED BOTH TO MAINTAIN SAID ANODE SUPPORT IN SPACED RELATIONSHIP TO SAID HEAT SINK AND TO ALIGN AXIALLY SAID PASSAGE OF SAID ANODE SUPPORT WITH SAID ALIGNMENT AXIS, (D) AN ELECTRON GUM FILAMENT INCLUDING AN APEX PORTION AND A PAIR OF DEPENDING LEG PORTIONS, EACH LEG BEING ELECTRICALLY CONNECTED WITH A DIFFERENT ONE OF SAID HALVES, SAID APEX PORTION BEING ALIGNED WITH SAID ALIGNMENT AXIS, (E) A GRID ASSEMBLY INCLUDING A PLATE-LIKE GRID HAVING A PERFORATION THROUGH ITS CENTRAL PORTION, SAID GRID BEING POSITIONED IN PROXIMITY TO SAID ELECTRON GUN FILAMENT TRANSVERSELY ACROSS SAID GUN AXIS SO AS TO HAVE SAID PERFORATION COAXIAL WITH SAID GUN AXIS, SAID ASSEMBLY FURTHER INCLUDING GRID SUPPORT MEANS EXTENDING FROM SAID HEAT SINK FOR POSITIONING SAID GRID AND FUNCTIONALLY ELECTRICALLY CONNECTING SAID GRID TO AN ELECTRICAL POTENTIAL, AND (F) AN ANODE OPERABLY ASSOCIATED WITH SAID ANODE SUPPORT GENERALLY COAXIALLY WITH SAID GUN AXIS. 